In a medical imaging system, the C-arm is a mobile arch which supports both the radiation source and the radiation detector. Radiation is usually X-ray. To provide images which can be simple photos, films, axial or lateral three dimensional, or four dimensional, or long three dimensional volumes thanks to helical acquisition, this C-arm can be moved and rotated along more or less complicated paths.
Medical imaging systems can be of different types. A Computed Tomography apparatus will capture one or several thin sections of a part of a human body and will provide a three dimensional image. An Interventional system will either provide a three dimensional image of a volume of a part of a human body or a film in a fluoroscopy mode. It can also provide a simple photo, which means a single shot. A Radiological system will provide a simple photo a part of a human body.
To check that no collision can occur with any object that would be on the trajectory of any part of the C-arm, most often in the prior art, a first move or rotation of the C-arm along the projected trajectory is performed at quite a slow speed, before performing it at high speed required to capture the needed images. This preliminary checking operation is laborious, all the more that it has to be performed often; indeed, and it has to be performed at least each time a new trajectory of the C-arm move is projected.
The main move of the C-arm will be a rotation around a virtual axis which roughly corresponds to the center of the C form of the C-arm. Since the C-arm is no full circle but only a part circle, when it rotates, and especially when it rotates at high speed, it means that any object crossing the trajectory of the rotation in the circular gap between the two ends of the C-arm will lead to a severe collision which should be avoided. Several prior art pieces have tried and tackled this collision avoidance in the gap of the C-arm during C-arm rotation, but none appears to be fully satisfactory.
According to a first prior art, for example described in U.S. Pat. No. 6,203,196, it is known a modular medical imaging system in which a full inner C of C-arm can be set up. Therefore, collision risk of an object coming in the gap of a partial inner C of the C-arm is successfully avoided. However, there is no efficient protection against other potential collisions, whatever the direction they are coming from. In some embodiments, the complementary part of the C-arm inner C is integral with the C-arm inner C, what makes the global system too cumbersome when the full inner C is not needed. Moreover, this integral structure with relatively mobile parts does not help with respect to vibration aspect.
According to a second prior art, for example described in patent application US 2003/0072416, it is known a modular medical imaging system in which a full protection outer C of C-arm can be set up. Therefore, collision risk of an object coming in the gap of a partial inner C of the C-arm is successfully avoided. Therefore, collision risk of an object coming from outward the C-arm is successfully avoided too. However, there is no efficient protection against some other potential collisions, especially when coming from inwards the C-arm inner C, what notably corresponds to the situation of body fluids, like for example urine or blood, projection from patient or from a moving part of a patient body, like chest or arm. In all embodiments, the outer protection cover of the C-arm inner C is integral with the C-arm inner C, what makes the global system too cumbersome when the full outer protection ring is not needed. Moreover, this integral structure with relatively mobile parts does not help with respect to vibration aspect.
According to a third prior art, for example a complete Computed Tomography apparatus, it is known a one piece medical imaging system in which a full protection inner and outer C of C-arm can be set up. Therefore, the collision risk is correctly tackled. But in many use configurations, the added complexity is much higher to the needed security requirements, what 10 practically makes this apparatus not usable or hardly usable for those use configurations. This apparatus is no multi-use apparatus but an apparatus dedicated to one type of image capturing mode.